Getting Hands-On| Practical Tips for TIG Welding Mild Steel

Setting Up and Preparing the Welder and Accessories

TIG welding mild steel can be done with the most basic of TIG welding machines. You can use a scratch start, lift start, or a high frequency power supply. The welder will need to be DC (direct current).

A 220 volt TIG welder with 200 amps can weld up to 1/4 inch or 6mm in a single pass at 200 amps. You will need argon shielding gas and the correct filler wire/rod and diameter for the carbon steel. I recommend ER70S-6 95% of the time.

Tungsten Inert Gas Welding Mild Steel Equipment Requirements

TIG Welder Power Supplies

TIG welding power supplies can be a TIG/stick machine with a lift or scratch start. This is what I started with, even when I was pipe welding. A 110-volt welder will get you up to around 140 amps if you need more welding current than that you will need a 220-volt welding machine.

TIG Torch

TIG torches sold for the DIYer are most commonly a 26 or sometimes a 17. These numbers are a standard to the maximum amperage. An air-cooled 17 torch will work well to 150 amps and a 26 is rated to 200 amps. These two torches can have the same collets, collet bodies, ceramics, and back caps/tailpieces. Air-cooled means the gas that flows through the torch is what cools it. Water-cooled torches are heavier and only needed for aluminum.

If you are just starting out I highly recommend a flex head for the TIG torch. I always fit them onto all my torches. They really help with getting the correct angle while making life a lot easier for you. They are not expensive and will speed up the learning process a lot.

Choosing The Tungsten Electrode Type

If you are going to be welding sheet metal panels on a car ie 20-22 gauge steel, I would suggest a 1/16th / 1.6mm anything over 16 gauge I use a 3/32 / 2.4mm tungsten. You can use the 3/32 by grinding them differently. As for the type of tungsten I recommend a 2% lanthanated, I have written all of the advantages of the electrode here. It is an all-rounder non-consumable tungsten electrode.

If you are doing a wide range of thicknesses you can buy a pack of ten with different sizes.

What Gas For Tig Welding Carbon Steel

The appropriate shielding gas for TIG welding carbon steel is Argon. This inert gas provides a stable welding arc, ensures optimal penetration, and yields superior weld quality when working with carbon steel.

That was easy 😎. The only thing to consider is the size of the bottle you need. Tig welding on steel requires a lot less gas than stainless, but by buying a bottle in the beginning you will need to be honest with yourself if you will need a larger bottle in the future for stainless TIG welding. I have a breakdown of the tank sizes available and how long each will last.

Argon Regulator

The gauges are a pretty cheap item. I recommend getting one with a flow meter. This is the tube with the ball that raises to show the argon gas flow rate. The twin dial type is for MIG welding that can require more gas usage, plus these have a larger pulse of gas when you first turn the flow on.

Mild Steel Filler Material 

ER70S-6 is my choice of TIG welding rods as mentioned before. This is an industry-standard mild steel filler rod for automotive, structural steel, or pressure vessels and can be used on Chrome moly/ chromoly (ER80S-D2 is ideal). The ER stands for electrode/rode the number 70 is the tensile strength of 70,000 psi and S represents its solid wire. The last number 6 is the chemical composition. In this case, the wire has higher amounts of silicon and manganese. This has a better cleaning property so a small amount or poor weld preparation can still be acceptable.

For anything below 1/16th  or 1.6mm, I would use a 1/16th TIG filler rod. For thicker materials, I always use a larger filler rod of 3/32 or 2.4mm.

Tools and Protective Gear Required For Welding Steel

I won’t go into too much detail here. You want to start welding, but a few things will speed up your welding progress. 

Additional Tools

• Welding Table: A heat-resistant, sturdy table or tassels to hold the workpiece.
• Wire Brush: To clean the surface of the workpiece before and in between runs.
• Welding Pliers: To trim the filler wire if you are having difficulty with it being so long. Or to remove the hot tungsten to resharpen it.
• Tungsten Grinder: To sharpen the tungsten electrode, this could be a bench grinder. Read the full guide on tungsten sharpening here.
• Clamps: To hold the workpiece in place during fabricating or welding.

Safety Gear

• Welding Helmet: To protect your eyes and face from sparks and intense light. With a shade range from 9 to 12. 9 for below 40 amps.
• Ear Protection: To protect your hearing from loud noises.
• TIG Welding Gloves: Heat-resistant gloves to protect your hands with high cuffs to protect your wrists.
• Safety Glasses: To wear under the helmet for additional eye protection.
• Safety Boots: Heat and spark-resistant boots to protect your feet.
• Respirator: To protect your lungs from potentially harmful fumes and dust.
• Fire Extinguisher: A safety measure in case of a fire.

TIG Welder Set Up 

Now you have all the correct gear let’s get the welder set up for great results.

Polarity For TIG Welding Mild Steel

When connecting the TIG torch to the machine will determine what polarity you will be tig welding. This is always the – negative. So the ground clamp is positive. Tungsten can handle a lot of heat but it requires the colder negative connection. This is also known as straight polarity.

While you are at the power source we can set the amperage.

I have a simple mild steel formula for every .001 of an inch use .8 of an amp so for example if you were welding some 1/8th inch or 3mm you would use 94 amps as a starting point. You can adjust higher or lower depending on the joint type. Fillet welds need more amps.

High Frequency Start Basic TIG Settings For Mild Steel

1. If you have a scratch, or lift TIG just skip this step if you want. But I cover a few points to help you avoid weld defects.
2. 2T or 4T: For tack welds, I use 2T and for longer welds, I switch to 4T. When gas tungsten arc welding with 4T you can shift your thumb off the button and get caught out trying to end the weld so be careful. If you have a foot pedal you are lucky.
3. Pre-flow: I suggest around 1/2 a second to get the surge of gas out before the arc starts.
4. Start current: I have this set to around 20 amps for anything above 18 gauge steel. This helps your eyes adjust to the welding arc and make sure you are in the weld area before the full amps kick in.
5. Upslope Time: The time the welder goes from start amps to the welding amperage you set.1 second is more than enough for me. Any longer I get bored.
6. Peak current: Use the TIG welding mild steel formula above to set this. This is the welding amps that you will be welding with unless you modulate it with a pedal or torch remote.
7. Downslope: This plays a big part of reducing crater cracks or pin holes with end current. I set my welder to a minimum of 3 seconds, this gives the molten metal weld pool to cool down gently. The thinner metals are more prone to pin holes.
8. End Current: A good rule of thumb is 10% of the peak current used.
9. Post flow: Even though carbon steel doesn’t need plenty of post-weld gas coverage the tungsten does. 5 seconds will be enough for below 100 amps. If you don’t have post flow the tungsten electrode will have contamination on it breaking it down and affecting future welds.

Setting Up The TIG Torch

I would recommend a flex head for TIG welding but it is not necessary. The following setup can be used with scratch, lift or high frequency TIG torches.

What Size TIG Cup For Mild Steel

Mild steel doesn’t require large gas coverage like stainless steel. I still like to use a gas diffuser, these can reduce the amount of argon you use. I will use a number 8 cup for mild steel welding. If I change the cup size it is to get into a tight spot.

Tungsten Stick Out For Carbon Steel

The tungsten stick out is limited by the ceramic cup used. The ideal maximum stick out is the inside diameter of the cup. So the number 8 we are using will have a stick out of 1/2 inch or 12mm. The tungsten can stick out further if you are welding on an included angle fillet weld.

Back Cap Selection

I use the long-type back cap on my tig torch because they can fit new tungstens in them without the need to trim them down. I have written on the best way to cut the tungstens down if you need to.

Gas Flow Rate For Carbon Steel TIG Welding

With mild steel, I run a little less argon than I have to. I don’t like getting my bottles refilled if I don’t have to. I have another formula for the gas flow rates for TIG welding.

The cup size will roughly require double the cubic feet per hour of Argon a number 8 cup will need 15 to 16 cubic feet an hour or 7 to 7.5 liters per minute. If you don’t use cubic feet an hour times the cfh by 0.47 and you’ll get liters per minute.

But like I said I use less for carbon steel so I would be happy to use 12 to 14 with a little less tungsten stick out. But for learning, being able to see keep it out to what I recommended.

TIG Welding Process Step By Step

In an effort to make this topic more accessible and straightforward, I’ll be supplementing this article with a helpful video demonstration in the near future. This additional resource will provide a practical, hands-on perspective to further facilitate your understanding. Keep an eye out for it! But the video on 7 Stainless tig welding faults does a good job for now.

For quality welds regardless if it is a butt weld, lap joint, or fillet weld the most important thing is a clean surface. Carbon steel rusts when old or can have mill scale when new. Use an angle grinder with a sanding pad or grinding disc to remove any paint or the mentioned above rust and mill scale.

Torch Travel Angle

• Angle the tungsten electrode and the torch in the direction of travel during welding.
• This angle allows for better visibility of the weld pool and improved control.
• By angling the torch, you create an oval-shaped weld puddle, which enhances penetration and fusion.
• Experiment with different angles to find the most comfortable and effective position for your welding technique.
• Finding the right torch angle facilitates better weld pool manipulation and overall welding performance.

Arc Length

• The arc length refers to the distance between the tip of the tungsten electrode and the surface of the workpiece being welded.
• It is important to maintain an appropriate arc length during TIG welding to achieve optimal results.
• The ideal arc length typically ranges from 3/64 inch (1mm) to 1/8 inch (3 mm), although it can vary depending on the welding conditions and material thickness.
• The arc length affects various aspects of the welding process, including heat input, penetration, and arc stability.

Significance of Maintaining the Gap

• Keeping the proper arc length is crucial for achieving a stable and controlled welding arc.
• If the arc length is too short (less than the recommended range), it can result in an unstable arc, tungsten contamination, and potential weld defects.
• On the other hand, if the arc length is too long (greater than the recommended range), it can cause excessive heat dissipation, reduced penetration, and an erratic arc.
• Maintaining the appropriate arc length ensures proper heat input and allows for effective control over the weld puddle.

Adjusting the Arc Length

• To achieve the desired arc length, you can adjust the distance between the tungsten electrode and the workpiece while welding.
• Use your hand and wrist movements to control the torch position and maintain the desired arc length.
• For consistent results, practice maintaining a steady arc length throughout the welding process.

Monitoring and Adapting

• During welding, it’s important to continuously monitor the arc length to ensure it remains within the recommended range.
• Factors such as joint configuration, material thickness, and welding position may require slight adjustments to the arc length.
• Be attentive to changes in the arc behavior, sound, and weld appearance, as they can indicate the need for arc length adjustment.

Controlling amperage If Using A Pedal

• Amperage control is crucial for achieving the desired weld characteristics and penetration.
• Adjust the amperage based on the material thickness and welding requirements.
• Use higher amperage when adding filler material, as it compensates for the cooling effect caused by the additional metal.
• Reduce the amperage slightly while moving along the joint to maintain consistency and prevent overheating.
• Effective amperage control ensures proper heat input and weld bead formation.

Maintaining A Consistent Travel Speed

• Steady hand movement is essential for producing a uniform and aesthetically pleasing welds.
• Avoid excessive shaking or abrupt movements that can affect the weld bead appearance.
• Practice maintaining a smooth and consistent travel speed along the joint for even heat distribution.
• Coordinate the movement of the torch and filler rod to achieve optimal control and precision.
• Developing a steady hand movement is key to achieving high-quality welds and reducing the likelihood of defects.

Adding Filler Material Into The Weld Puddle

• When using filler material, carefully introduce it into the leading edge of the weld puddle.
• Dip the filler rod at a slight angle to allow it to melt and fuse with the base material.
• Avoid crossing the arc with the filler rod, as it can lead to contamination and affect the integrity of the weld.
• Proper filler material usage ensures stronger welds and effective bonding between the base metal and filler.
• Practice controlling the filler rod and its position relative to the weld puddle for consistent and high-quality welds.

Troubleshooting Welding Mild Steel With TIG

Getting Porosity When TIG Welding Mild Steel

Porosity in TIG welding mild steel typically stems from four main issues: incorrect/dirty filler metal, improper shielding gas coverage, excessive heat, and dirty base metal. For optimal, porosity-free welds, select the right filler, manage gas and heat appropriately, and thoroughly clean your mild steel beforehand.